What is the distance formula?

d = √[(x₂−x₁)² + (y₂−y₁)²] — Pythagoras in coordinates. The midpoint is the average of each coordinate.

How do I find the distance from a point to a line?

Write the line as Ax+By+C=0; then d = |Ax₀+By₀+C| / √(A²+B²). The foot of the perpendicular and the reflected point are given too.

How can I tell whether three points are collinear?

Compute the triangle area — zero means collinear. The tool uses the cross product: S = ½|x₁(y₂−y₃) + x₂(y₃−y₁) + x₃(y₁−y₂)|.

When is the slope undefined?

When the two points share an x-coordinate the line is vertical and has no slope; the equation is written x = constant and the tool says so explicitly.

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🧭Coordinate Geometry Calculator - Distance, Midpoint, Slope and Line Equations

The coordinate geometry you need most often: distance, midpoint, slope, line equations and the perpendicular bisector from two points; distance, foot of the perpendicular and reflection for a point and a line; area, collinearity, centroid and circumcircle for three points; plus conversion between polar and Cartesian coordinates.

Free · No sign-up · Runs in your browserLast updated: 2026-10-26

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How to use Coordinate Geometry

1Choose two points, point and line, three points, or polar conversion
2Enter the coordinates, or the A, B and C of the line
3Read the results and the formula, and copy what you need

FAQ

What is the distance formula?: d = √[(x₂−x₁)² + (y₂−y₁)²] — Pythagoras in coordinates. The midpoint is the average of each coordinate.
How do I find the distance from a point to a line?: Write the line as Ax+By+C=0; then d = |Ax₀+By₀+C| / √(A²+B²). The foot of the perpendicular and the reflected point are given too.
How can I tell whether three points are collinear?: Compute the triangle area — zero means collinear. The tool uses the cross product: S = ½|x₁(y₂−y₃) + x₂(y₃−y₁) + x₃(y₁−y₂)|.
When is the slope undefined?: When the two points share an x-coordinate the line is vertical and has no slope; the equation is written x = constant and the tool says so explicitly.